


Evolution

by KathrynShadow



Category: Rockman X | Mega Man X, Rockman | Mega Man - All Media Types
Genre: Friends to Lovers, M/M, Sleepy Cuddles, Slow Burn, Tumblr Ask Box Fic, Unresolved Sexual Tension, X says long words when he's nervous, but only in chapter one sorry
Language: English
Status: Completed
Published: 2014-02-12
Updated: 2014-02-12
Packaged: 2018-01-12 02:21:18
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 5
Words: 4,591
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1180767
Author URL: https://archiveofourown.org/users/KathrynShadow/pseuds/KathrynShadow
Summary: <blockquote class="userstuff">
              <p>“I don’t—” he says to the old scientist before trailing off. Don’t what? Like newbies? He’s fine with ‘em as long as they give a shit about what they’re doing. Train people? He’s done it before.</p><p>Dr. Cain sighs, bringing a wrinkled hand up to rub his wrinkled forehead. “I know it’s been difficult for some of the other Irregular Hunters to come to terms with you—”</p><p>"That isn’t the point." But it kind of was. The first reploid murderer—not exactly the kind of person you wanted in an ally… "…sir," Zero added belatedly, realising his interruption.</p><p>Dr. Cain waved off the honorific with an irritated huff. “X trusts you,” he said. “So do I.”</p>
            </blockquote>





	1. Chapter 1

It’s pretty common knowledge that X has been through several attempts at combat training so far—“attempts” being the operative word. Zero doesn’t really keep up with Hunter gossip or any gossip at all, really, so he doesn’t know what keeps happening between the scientist and his CO’s. He _does_ know that he’s probably the last person anyone but Sigma and Dr. Cain would want around The Father Of The Entire Race (angelic chorus optional), so when X is assigned to him, he figures it’s probably as a last resort.

_(“I don’t—” he says to the old scientist before trailing off. Don’t what? Like newbies? He’s fine with ‘em as long as they give a shit about what they’re doing. Train people? He’s done it before._

_Dr. Cain sighs, bringing a wrinkled hand up to rub his wrinkled forehead. “I know it’s been difficult for some of the other Irregular Hunters to come to terms with you—”_

_"That isn’t the point." But it kind of was. The first reploid murderer—not exactly the kind of person you wanted in an ally… "…sir," Zero added belatedly, realising his interruption._

_Dr. Cain waved off the honorific with an irritated huff. “X trusts you,” he said. “So do I.”)_

X looks exhausted when he and Zero meet as Hunter and prospective Hunter for the first time. Zero saw him a few times before—a lot early on, when Zero was still playing lab rat—but never looking that drained; the scientist’s eyes look a little greyer than normal, his lips pressed together in a tight line, his skin actually managing to look artificial for once without the constant thrum of circulatory fluids buzzing at the surface.

Zero doesn’t ask.

X gives him a tiny, weary smile. “Please don’t worry about hurting me,” he says, and he has the air of someone beginning a speech.

“I’m not supposed to,” Zero interrupts, frowning a little. “Babying you isn’t going to help anyone.”

Visibly, X sags a little in relief. “ _Thank you_ ,” he says, fervently. “I thought everyone in the Hunters was scared of breaking m— _eep!_ ”

Zero lunged midsentence, beam sabre slicing into sudden life as he dashed to close the distance.

Squeak of alarm aside, X’s reflexes aren’t so bad. He snaps his buster arm up as he stumbles blindly back, instinctively firing a few quick shots—a couple of them hit Zero’s shoulder, where they sting and singe but don’t do any real damage. The berserker grimaces as the energy scatters across the burnished metal of his breastplate, a couple of sparks grazing his cheek. It doesn’t even slow him down, and in a couple of strides he leaps, slamming feet-first into the shorter reploid. He knocks X to the ground and they hit the floor hard, X in an ungraceful sprawl and Zero in a crouch. His left knee pins X’s buster arm to the tiled floor and the blade of his sabre thrums a micrometer away from the unguarded flesh under X’s chin.

X swallows. Slowly. Zero lets himself breathe.

"You didn’t warn me," the blue reploid says weakly.

Zero grins as he rocks back on his heels. “Wasn’t that the point?”

X laughs as he sits up, rubbing the back of his helmet self-consciously. He accepts Zero’s help getting back to his feet, but the moment he’s stable again he skips back a couple of steps, a charge already beginning to gather in his half-raised buster.

The blond Hunter gives a feral smile. “What’s wrong, X? I thought you trusted me.”

“With my life.” X grins wryly, steadying his stance, his charge levelling off in a steady hum. “Not so much my dignity.”

Zero is still smiling, fiercely and genuinely, even as he circles to the side to line up a second attack.

He is not used to trust. Even with Sigma, Zero is a calculated risk; Dr. Cain pities him, which is almost worse, but… but this… this is—new, and—good.

X startles him by shooting unprovoked and dodging to the side before Zero can do anything about it. It’s just a glancing blow, really, but it hits and it knocks him back a few feet, and he intentionally falls to one knee and winces, just to see what will happen.

Silence. “Zero?” A hesitant footstep—two—and a tiny, worried breath. “Zero, are you okay? I’ve never used the full charge before, so I wasn’t sure—”

A third step.

Zero launches himself forward, flicking the blade of his saber off a half-second before he brings his arm forward in a vicious stab to X’s abdomen—

And X’s buster is up and charging and aimed at his face.

X looks downright jubilant. “I _thought_ you were bluffing.”

Zero raises an eyebrow. “I still gutted you.”

“I still shot you in the face.”

“I can come back from that.”

X jerks his head towards the now-silent hilt of Zero’s sword. “I can come back from _that_.”

Slowly, Zero straightens, saber now pointed towards the scarred tile floor. X lowers his arm to his side, the buster’s charge dispersing harmlessly across its shell.

Zero grins. “Guess we both have to try harder, then, huh?”


	2. Chapter 2

**Summary for the Chapter:**

> Funny, Zero never really thought he would die for X until he was in the middle of doing it.

Funny, Zero never really thought he would die for X until he was in the middle of doing it.

Not that he’d ever assumed he wouldn’t. He hadn’t thought about it much at all, really. Or ever. And yet, when he sees X crumpling to one knee, gritting his teeth in pain, armour sparking from the dozens of cuts and dents in its surface (thicker, darker internal fluid running from some of them where the armour wasn’t enough), trying so hard to keep himself upright as Vile’s electrical field crackles around him—

Zero’s as surprised as they are when he wrenches his cage open.

(The pain is incredible. Error messages flash and pulse and pixellate across his vision overlay; attacking his prison directly sent a vicious current through his core, and he can feel his components frying despite all his shielding. But, well, judging by those error messages he’s got about two minutes before he goes into emergency shutdown, and he won’t be any use to X if he’s unconscious. And anyway, it’s just unspeakable agony. He’s had worse.)

Most of him isn’t working, nonessential systems shutting down one by one, but the inherent problem with that is that his combat systems are technically “nonessential” at this level.

Zero doesn’t even need to think about it.


	3. Chapter 3

**Summary for the Chapter:**

> X is different when Zero comes back.

X is different when Zero comes back.

The berserker doesn’t say anything, of course, because he rarely says anything that isn’t some form of snarky comeback (at least, not when he’s happy). X doesn’t need him to. He knows, and he knows Zero knows, and he’s pretty sure Zero knows that too. So they just sort of… don’t say anything. For a long time. X grabs Zero’s hand as the fortress is exploding behind them, squeezing it too hard to be comfortable for either of them, but Zero doesn’t pull his hand away. Squeezes back. Just a little.

They don’t talk, but Zero doesn’t leave X alone, and X doesn’t know how his friend knows but he is so, so grateful for it. For someone with the social aptitude of a lead brick, Zero has some pretty startling insight sometimes, with some people. Well, X has only seen it happen with himself, but there’ve got to be others. They’re friendly—could even be described as close, by some definitions, especially now—but X can’t possibly be the only person Zero can understand like that. Zero joined the Hunters months before the possibility had even crossed X’s mind, for goodness’ sake…

"That was really dumb," Zero says suddenly, interrupting X’s mental ramblings. The blue bomber looks over at him. Zero is lounging across the immensely uncomfortable medbay couch, casually taking up enough space for at least four of himself. He’s staring up at the ceiling (not at the wires, or the tools, or the diagnostic equipment; he never was completely at ease around repair wards), one armoured foot absently jiggling up and down to a rhythm only Zero can hear.

X is so distracted focussing on how wonderfully, beautifully alive his partner is that he almost forgets that he’s supposed to respond. “What was?”

"Getting my parts back." Zero glances down to look at him. "Talked to Dr. Cain when he was putting me back together."

X feels vaguely like a rookie who just got caught in the top-security labs. “What do you mean?”

Zero raises an eyebrow. “Are you kidding? That setup had ‘trap’ written all over it, and don’t even try to say you didn’t notice.”

X looks off to the wall, fidgeting with the wire connecting him to the power supply for his auto-repair. “It was worth it.”

Zero is quiet for a few seconds. “So were you,” he says, finally.

Months. Months of fighting, of killing, of slaughtering, of watching his fellows get slaughtered in turn—months of horror and dread and awful, awful doubt—all at once, it all comes crumpling down on him. His shoulders shake first, and then his lips, and he has just enough time to draw one knee up to his chin in a haphazard attempt at the foetal position before he just starts sobbing.

Zero is off the couch and on the repair table next to him before he can breathe. The berserker is talking, and he sounds worried—scared—but X can’t hear the exact words, just knows that Zero of all people is alive and he couldn’t bring back any of the others but here, here is one person, one person he could save—

He feels the diagnostics of the repair ward reaching out to him, probing down his neural passageways, and he starts laughing with delight and relief and some sort of crazed madness because Zero, sweet Zero, silly Zero, worried about him for crying—

"I’m shutting you off for now," Zero tells him in the handful of seconds when X pauses his breakdown to gasp in a breath.

X doesn’t need to ask.

"I’ll be here when you wake up," the red terror murmurs, awkwardly ruffling X’s mussed tangle of hair. "I promise."


	4. Chapter 4

**Summary for the Chapter:**

> True to his word, Zero is still there when X wakes up from the emergency shutdown.

True to his word, Zero is still there when X wakes up from the emergency shutdown.

Quite there, actually; he must have followed X down when the shorter reploid collapsed, hooking an arm behind X’s head—as if X could even feel discomfort when switched off, and as if Zero’s armour would be any more comfortable than the table anyway!—and lying at his side. (Just in case touch was the first sense to come back on, X guesses, and holds back a goofy kind of happiness at that thought.) Zero’s head is pillowed on X’s chest now, his body curled reassuringly around X’s, his hair covering them both like the most ineffective blanket in existence. His knee is somehow wedged between X’s own, their feet tangled, hardly any space left between them. Zero’s—Zero’s practically cuddling him, and X wants to laugh just at how absurd that would have sounded even twenty-four hours ago, but he doesn’t.

He doesn’t, because Zero is also very, very offline. His eyes are half-lidded, their backlighting off. He breathes maybe once every sixty seconds just to get rid of the minuscule bit of heat from his background processes. X can feel—through the same network of empathy nanites that power his copying ability—Zero’s own diagnostics and auto-repair functions busying themselves, tidying up the loose ends from his admittedly rushed reconstruction.

Not that Zero had helped any, running off like that the second he heard X was in trouble…

X fights the goofy happiness again, and he tucks an arm against Zero’s back so he isn’t twisting his spine so awkwardly, and with his free hand he brushes a few stray hairs away from Zero’s face, and then he leans just a little bit forward and presses a warm kiss to the top of Zero’s head.

He stills.

X is an affectionate person. He hugs, he pats, he bestows little friendly touches on pretty much anyone not trying to kill him at the time. Nothing he has just done is out of the ordinary for him with anyone he holds dear.

But it feels out of the ordinary. Or perhaps it feels out of the ordinary for feeling so ordinary—he can’t tell. Whatever it is, it’s changing the way he’s processing his responses to his own actions, and that’s… that’s interesting. X had catalogued all of the main emotions within his first week of life, but even just discovering new mixes and subspecies was exciting, and it hadn’t happened in such a long time—

—and the last time was with Zero too, wasn’t it? Because he’d known pain, he’d known grief and loss and all the side-effects of bereavement, but Zero’s sacrifice had just been too close, the death of a constant, like gravity itself had stopped working, so desperately bewildering—

—and that, that was definitely worth pursuing. Especially since he had an unconscious lump of metal-encased metal lying half on top of him and he wasn’t going to be moving anytime soon.

When X doesn’t understand something, he reads. He prefers physical books—he’s not completely sure why, just a way humanity rubbed off on him, he supposes—but, again, he can’t move. And even if he could, he wouldn’t want to disturb Zero even if it is nonessential maintenance…

(X purses his lips, mentally jotting that down for future reference.)

Technically, he could just download and instantly parse the text of anything he could find in the network. It definitely has its uses—particularly when it comes to the unreasonable amount of paperwork that apparently comes with multiple wars—but not… not right now. Right now, he wants to think about things, and he wants to take more time than he strictly needs to.

So he shuts his eyes, filters through an entire virtual library, pausing over some things and downloading others.

(A few of the books, he downloads and gets a few pages in only to delete them. Lust is an interesting concept, but it isn’t what he’s looking for. X isn’t even sure reploids are capable of it, come to think of it… there’s certainly no reason for it, but technically there wouldn’t be a reason for a lot of the things his kind are capable of…)

He reads the complete works of Jane Austen and likes them much better. He takes a stab at the Bronte sisters. He briefly wanders over to Romeo & Juliet, but discards it as off-topic before wondering why it was tagged as romance in the first place.

He doesn’t find anything… concrete. But he finds a lot of impressions, and the symptoms are described at multiple points in different ways, and while he can definitely disregard many of their manifestations as not applying to him, there are some others…

X opens his eyes again and looks thoughtfully at the ceiling. Then, more thoughtfully, down at Zero’s sleeping face.

Zero looks… calm. Relaxed. Almost younger—not boyish, not with his chassis’ replicated age, but less… old, a quality that X had never even noticed in his friend until now that it is gone.

Zero looks calm. He looks calm lying there, asleep, holding X.

X shuffles down a little, nosing Zero’s hair, holding him just a little bit closer than before. Zero is much softer than he looks, his metal skeleton covered in layers of protective padding and artificial muscle, and when he is still he is as soft to the touch as any human. But there isn’t that strange, uneven heartbeat, that quickens and slows and judders like it’s about to give out any second even at its healthiest; there’s the slow, steady background hum of slumbering machinery, unchanging until something changes it. It’s—it’s nice. All of this is nice.

X nibbles on his lip and studies Zero’s face and wonders if Zero’s mouth is as nice to touch as the rest of him seems to be. Wonders if kissing would have any meaning to him, if it would have any effect, fully asexual reproduction rendering mating rituals and subtle genetic compatibility testing pointless.

But it sounds good, the way the humans talked about it. And he thinks—he thinks that if he were going to test it out, he’d like to perform that test with Zero.

X closes his eyes and develops a hypothesis.


	5. Chapter 5

**Summary for the Chapter:**

> “I’m not going to forget about you, you know.”
> 
> “What do you mean?”

_"Zero?"_

_"Yeah?"_

_A thoughtful narrowing of eyes, an entire silent conversation held with a nearby wall. “Do you think we’re—reploids, I mean—do you think we’re capable of romantic emotion?”_

_Zero raises an eyebrow, smirking a little. “Are you asking me on a date?” he teases._

_X’s face erupts in a lopsided, splotchy blush. “I’m just—curious about what you think about the subject. We’ve seen platonic bonds in action, which make sense from a survival standpoint as well as the cooperation my creator intended to cultivate between our species and his, but installing the capability for romance would be redundant to that point, and we don’t need it for reproduction. On the other hand, he did design me to be—fully auto-customisable, in a sense, and he could have given the basic parameters in case I felt like using them…”_

_Zero speaks before X has a chance to babble out an entire essay. “Isn’t your last Navigator dating—oh, what’s her name, down in the repair ward?”_

_X looks at him doubtfully. “I didn’t think you kept up with Hunter gossip.”_

_"I don’t. Douglas does."_

_X snorts a laugh. “You wouldn’t have to listen nearly as often if you weren’t as rough on your equipment,” he teases. And just like that, the subject is changed, and the conversation moves on, and Zero thinks nothing of it._

—

Zero is looking for X.

Funny; they’ve gotten to the point where he doesn’t even need to say that anymore. Other reploids just notice him walking down the same halls a few times alone and just assume that he’s looking for his partner.

He likes to snark back, snipe that he has no Light Number-centric separation anxiety, that he is fully capable of functioning without X in the room, thank you very much, but he doesn’t do that as often as he usually would. Mostly because he usually _is_ looking for his friend.

This time, though, his cohorts’ directions either are inaccurate or take the form of helpless shrugs and a few weak conjectures. Not too surprising—X is a pretty private person, yeah, sometimes he’ll just slip off—but really, really not the time.

—

_Three weeks after they have that conversation, Zero meets—and subsequently gets assigned to—Iris. And Iris is—determined and hopeful, like most, but she’s also not scared to (politely) call Zero out on his shit or (gently) rip him a new one when he steps too far out of line. And that makes her interesting in a way that most Navigators aren’t, to him._

_(It’s supposed to be a symbiotic partnership, something fuller than an assigned alliance between soldier and communications officer, but Zero’s not good at… those. At people. …At people who aren’t X.)_

_Iris is interesting, and she doesn’t die within her first week or even her first month. Zero doesn’t realise that they’re friends until X points it out to him, doesn’t even contemplate the possibility that there might be something else to it until he catches her blushing once or twice. But once **that**  happens, after Douglas not shutting up and X having theories, he sort of—maybe—starts thinking about Something Else. And, well, humans aren’t exactly renowned for their infallibility, but when almost the entire species agrees on something, even Zero has to listen._

_Iris is—Iris is kind of cute. Kind of really, really cute. So there’s that._

_Thank God she kisses him first, though, or he would have spent another month and a half trying to figure out how to go about it._

—

X doesn’t seem to be… anywhere. And Zero has the same security clearance that the blue bomber does, so it isn’t as if there’s a place X could be that Zero _couldn’t_.

So he’s not in HQ or its immediately surrounding satellite buildings. And frankly, Zero can’t blame him—the complex was dreary enough, but after watching the Fourth War erupt practically within its walls, so many Repliforce agents living with the Hunters out of convenience…

Zero wants to just slip into X’s room and take a nap until his friend gets back, but even if he technically has permission to do that whenever he feels like it, X wouldn’t have gone off the radar even momentarily if he felt like being around anyone. So Zero scribbles a note on the back of the previous year’s Christmas list—

—a silly little quirk of X’s, he loves human holidays, somehow gets half of the Hunters to join in on most of them, and Zero of course was always hopeless—

—and slips it under X’s bedroom door before wandering off again.

Hopefully his partner won’t be too long with whatever he’s doing. This is kind of important.

–

_Zero figures he probably doesn’t need to tell X about him and Iris being—whatever it is that they’re being, because X most likely knew before Zero even did. And when X glances over and sees them holding hands, Iris laughing softly at something and bumping her head against Zero’s shoulder, he doesn’t look surprised. But there is—something. Not a flinch, or a break, or anything Zero even has a word for—but there’s a pause, and X blinks, and then something seems to settle inside him and he nods. Just a little, just once, to himself. Like something has been Decided._

_And then he glances up to see Zero looking at him, and he grins, quickly enough that the berserker isn’t completely sure that there even was an expression before that, and he raises his eyebrows teasingly._

“ _Shut up,” Zero mouths at his friend, resolutely looking the other way and trying to stop the faint prickle of embarrassment crawling up his neck. X is going to have a field day with this after how dismissive Zero was of the whole romance thing the first time. Shit._

_Iris squeezes his hand and smiles up at him, and he can’t not smile back, just a little._

_…Okay, he thinks, kissing her temple quickly. This is worth it._

–

Zero is almost asleep when his door clicks open. There are two gentle knocks on the frame and then, in a quiet voice, “Zero?”

X. Zero tries to kickstart himself back into full processing power immediately and gets an error message and a flash of pain behind his eyes for his trouble. Wincing, he pushes himself up so he’s sitting in his recharger, blinking until the static goes away. “Here,” he says.

Gentle footsteps on the clean floor; X isn’t wearing his armour. Not surprising, really. “Are you okay?”

“I’m fine, X. Relax.” Zero snorts, peering up at his friend. “You were the one who disappeared.”

X looks away, shrugging a little, his mouth twitching in something like a grimace. “They put a park back together,” he says. “I hadn’t seen it since it, uh.”

Zero thinks about trying to be reassuring, but he isn’t exactly sure how. “What’s it like now?”

X chews on his bottom lip. “The birds haven’t come back,” he says finally, “but there were some green parts.” He smiles, wearily. “What did you want to see me for, Z?”

“Uh.” Zero rubs his eyes. Damn, he had a… he had a _speech_ planned out, practically. “I was thinking,” he says finally.

X’s lips twitch. “Should I alert the media?”

Zero pauses in his partial reboot to glare at his friend. “You,” he says sternly, “have been hanging around me too much. I thought you were the polite one.”

X grins.

–

“ _I’m not going to forget about you, you know.”_

“ _What do you mean?”_

–

“I’m sorry,” the brunet says, half-perching on the edge of the recharger capsule, absently swinging the leg that isn’t still resting on the floor. “What were you thinking about?”

Zero picks at his thumbnail, wondering—not for the first time—why he even has those. He wasn’t built to be able to hide, like X was, after all. “Do you remember our conversation a few months ago, when you asked if I thought reploids could…?”

X snaps his gaze down, his brow furrowing. “Iris’s death wasn’t your fault,” he says. “You know that, right?”

Zero tries not to wince. “I know you believe that,” he offers—the best he can do. “But I wasn’t thinking about that this time.”

X tilts his head, but still looks worried. “You’re missing her?”

“I—yes, but—” Frustrated, the blond growls a little, flicking a flyaway strand of hair from his face. “ _Damn_ it, X, that isn’t what I’m trying to say…”

–

“ _I meant… since I had a girlfriend, I thought you might be… concerned.”_

_A sudden laugh like—like summer rain, or something, all at once and refreshing and shocking a breath into you just by how happy you are that it exists, but that sounds like a stupid thought the moment it crosses Zero’s head. “Of course not, Zero. But thank you, anyway.”_

–

X pulls his legs in to fold them underneath his body, still frowning but more in bemusement than anything else now. “Well—you already gave me the answer to my question,” he says, puzzled.

“Yes, but…” This sounded like such a good idea a couple of hours ago. “You sounded like you wanted your own evidence if you could get it.”

“If I could get it, yes,” X echoes doubtfully, “but you know how long… I end up knowing… most people.” He shrugs a bit, gives a little half-smile. “Besides, by some definitions, most of them are my children.”

Zero learned, through his unfortunately short-lived relationship with Iris, that he is not very good at flirting.

“I’m not,” he says.

–

_Oh. “I thought you looked…” He fumbles for a word. “A little upset, or something.”_

“ _Zero.” His friend sighs, gives him a look that somehow conveys both an infinity of patience and an infinity of weariness at the same time. “I’m **glad** about you and Iris. You’re happy, so I’m not upset.”_

“ _I didn’t think you would be. I just… wanted to make sure you knew that she wasn’t…”_

“ _Replacing me?” X snorts in amusement. “We’re partners, Zero. It’s different. I know she isn’t.”_

“ _Good.”_

–

“I mean, if you wanted a… test subject,” Zero adds, quickly, “then I’d be… okay with that.”

He tries to figure out what emotions are in X’s expression. He fails miserably. “Why?” X asks carefully.

–

“ _…She couldn’t replace you anyway.”_

–

Zero frowns. “Because,” he says.

X chews his lip thoughtfully. “I don’t think test subject is a good term,” he muses. “We would both be parts of the experiment. I wouldn’t only be observing.”

–

“ _Nobody could.”_

–

X cocks his head at Zero, curious. “What do you think about being my lab partner instead?”

–

“ _I love you too, Zero.”_

–

Zero chuckles, resting his forehead against X’s ribs, something warm and relaxed and familiar unfolding inside him at the closeness. “I’d rather be your lab rat than anyone else’s,” he says wryly, “but I think I would like that better. Thanks.”

–

“ _I know.”_


End file.
